This invention relates to rail pullers, and more particularly to hydraulic clamping rail pullers used to tension rails.
Rail pullers are commonly used in railways to pull the ends of rail sections together. Rail sections are relatively long, and may be as long as one quarter mile. The rail sections are usually aligned linearly with a gap between the ends of the rail sections. The gap between the rail sections may be approximately 6 inches. The rail puller puts the rail sections in tension to reduce the gap between the rail sections. Once the rail sections are pulled together, the ends of the rail sections are welded together to form a continuous track.
Rail sections are relatively heavy, and the force required to pull rail sections together and reduce the gap between the rail section is relatively large. Some prior art rail pullers use rams or hydraulic cylinders to pull the rail sections together. The hydraulic cylinders needed to generate the relatively large force required to pull the rail sections together are relatively heavy and expensive. Two characteristics of hydraulic cylinders are the travel distance and the pull capacity of the cylinder. The travel distance is dependent upon the length of the cylinder, and determines the distance between the fully retracted cylinder to the fully extended cylinder. The pull capacity is related to the cross-sectional area of the cylinder, and determines the amount of force the cylinder can generate.
Rail pullers generally clamp the rail sections, and then pull the rail sections together. The force required to clamp the rail sections is significantly less than the force required to pull the rail sections together. In some prior art rail pullers, the same hydraulic cylinders are used to both clamp the rail sections and pull the rail sections together.
The rail puller embodying the invention applies tension to rail sections to reduce the gap between the ends of rail sections. The rail puller comprises a first clamp assembly at one end of the rail puller, and a second clamp assembly at the opposite end of the rail puller. An elongated clamping beam is coupled to the first clamp assembly and the second clamp assembly, and includes a clamping cylinder that is extendable and retractable to adjust the length of the clamping beam. Elongated pulling members are coupled to the first clamp assembly and the second clamp assembly, and each pulling member has a pulling cylinder that is extendable and retractable to adjust the length of the pulling member. The clamping cylinder extends to position and clamp the first clamp assembly and second clamp assembly to rail sections, and the pulling cylinders retract to draw the first clamp assembly and second clamp assembly toward one another and reduce the gap between the rail sections.
The rail puller minimizes the travel distance of hydraulic cylinders used to pull the rail sections together. The clamping cylinder extends to lengthen the clamping beam and clamp the clamp assemblies onto the rail sections. Once the rail sections have been clamped, the pulling cylinders retract to pull the rail sections together. The travel distance of the pulling cylinders is reduced because the clamping cylinder is used to clamp the rail sections. Since the travel distance of the pulling cylinders is reduced, the weight and cost of the pulling cylinders is also reduced.
The force required to position the clamp assemblies clamp the rail sections is significantly less than the force required to pull the rail sections together, and the pulling capacity of the clamping cylinder can be substantially less than the pulling capacity of the pulling cylinders. Additionally, a single clamping cylinder can be used to clamp the rail sections. Since the pulling capacity of the clamping cylinder can be less than the required pulling capacity of the pulling cylinders, the overall weight and cost of the rail puller can be minimized.